Make sure the original ClassLoader is restored when running HCatalog tests

Details

Description

When Sqoop runs in test mode it creates another ClassLoader that loads from the generated JAR file in addition to everything else currently on the classpath (see: com.cloudera.sqoop.util.ClassLoaderStack#addJarFile) so it is dependent of Thread.currentThread().getContextClassLoader() value.
However in HCatalog test cases Sqoop invokes org.apache.hive.hcatalog.cli.HCatCli#main method directly in process (org.apache.sqoop.mapreduce.hcat.SqoopHCatUtilities#executeHCatProgramInProcess) which can override the contextClassLoader in the current thread and cause the tests to fail.

The task is to improve org.apache.sqoop.mapreduce.hcat.SqoopHCatUtilities#executeHCatProgramInProcess to make sure that the class loader used before invoking HCatCli is restored after the main method of the CLI is finished.